Traditionally, water-absorbent clays have been relied on for use as animal litters. The problem with certain of these conventional water-absorbent clays is that some tend not to absorb noxious odors as the waste products biologically break down. Eventually, as the waste products accumulate, the odor increase requires that the entire litter charge be replaced.
Recently, "clumpable" animal litters have become a popular method of reducing the build up of waste odors. With clumpable animal litters, urine is agglomerated with an absorbent material into a clump of material that may physically be removed from an animal litter box. Provided the urine clumps and other waste products are periodically scooped away, saturation of objectionable odors is avoided. This clumping aspect also allows only the specific litter affected to be removed, thus a bulk of the litter charge is retained for subsequent use.
To date, there have been essentially two types of clumpable animal litters. The first type of clumpable animal litter contains predominately smectite or other hydrophilic clay types such a bentonite or palygorskite group clays. An example of a bentonite clay-containing cat litter is provided by J. Hughes in U.S. Pat. No. 5,129,365. A problem with smectite clays is that some pet owners ignore instructions not to flush the clumps down a toilet. Water-swellable clays that have a tendency to increase as much as 10 to 14 times by volume can cause severe sewer problems if introduced or concentrated in large enough quantities. Another potential problem with clay-based clumpable animal litters is "dusting" that occurs during the pouring of the litters into the litter box container.
Several additives for improving clumpability of smectite clay have been proposed. G. A. Stuart, in U.S. Pat. No. 4,685,420, discloses the use of a particulate water absorbent polymer in combination with a clay based animal litter for agglomeration. Similarly, T. Fujimori, in Japanese Pat. Publication No. 1-191626 discloses use of an acrylic acid vinyl alcohol copolymer or a sodium acrylate polymer, powdered paper and bentonite mixture for forming clumpable animal litters. Finally, T. M. Kiebke, in U.S. Pat. No. 5,216,980, has recently disclosed use of a semolina additive to clay particles for creating a clumpable cat litter. However, these clays continue to rely upon water swellable clay as the base material.
In addition to the clay based animal litters, alternate clumpable mixtures have been proposed. For example, H. Wakamiya, in Japanese Pat. Publication No. 63-219323 discloses a mixture of sand and at least 15 wt % ferrous sulfate monohydrate for forming removable clumps. H. R. Loeb, in U.S. Pat. No. 5,152,250, discloses use of granulated peanut shells, flour and mineral oil for holding the mixture together. It is believed that these clay alternatives have not been commercially successful.
It is an object of this invention to provide a smectite-free clumpable cat litter.
It is a further object of the invention to provide an all natural clumpable animal litter.
It is a further object of the invention to provide a substantially dust-free animal litter.
It is a further object of this invention to provide an animal litter capable of forming durable removable clumps in a few minutes.